Catheter support for stent delivery

ABSTRACT

An angioplasty and stent delivery system to facilitate introduction and placement of a stent, including a catheter having an expandable distal portion constructed and arranged for expanding the outer diameter of the catheter from a contracted state to an expanded state: a stent positioned around the distal portion of the catheter having a contracted condition and being expandable to an expanded condition, and being sized in the contracted condition to closely surround the catheter in the contracted state, the expandable distal portion of the catheter including a balloon within which or over which there is included on a catheter shaft at least one axially movable or enlargeable body of a diameter larger than the catheter shaft to which the stent and balloon are fitted, as by crimping, for holding the stent in place until it is released therefrom by expansion of the balloon.

This is a Continuation-in-Part application based on U.S. Ser. No.08/702,150 filed Aug. 23, 1996, entitled STENT DELIVERY SYSTEM and aContinuation-in-Part of U.S. Ser. No. 08/697,453 filed Aug. 23, 1996,entitled PRE-MOUNTED STENT DELIVERY DEVICE WITH INFLATABLE TUBECOMPONENT.

BACKGROUND OF THE INVENTION

In typical PTCA procedures, a guiding catheter is percutaneouslyintroduced into the cardiovascular system of a patient through a vesseland advanced through therein until the distal end thereof is at adesired location in the vasculature. A guidewire and a dilatationcatheter having a balloon on the distal end thereof are introducedthrough the guiding catheter with the guidewire sliding through thedilatation catheter. The guidewire is first advanced out of the guidingcatheter into the patient's coronary vasculature and the dilatationcatheter is advanced over the previously advanced guidewire until thedilatation balloon is properly positioned across the lesion. Once inposition across the lesion, the flexible, expandable, preformed balloonis inflated to a predetermined size with a liquid or gas at relativelyhigh pressures, such as greater than about four atmospheres, to radiallycompress the arthrosclerotic plaque of the lesion against the inside ofthe artery wall and thereby dilate the lumen of the artery. The balloonis then deflated to a small profile so that the dilatation catheter maybe withdrawn from the patients vasculature and blood flow resumedthrough the dilated artery.

In angioplasty procedures of the kind described above, there may berestenosis of the artery, which either necessitates another angioplastyprocedure, a surgical by-pass operation, or some method of repairing orstrengthening the area. To prevent restenosis and strengthen the area, aphysician can implant an intravascular prosthesis, called a stent, formaintaining vascular patency inside the artery at the lesion. The stentis expanded to a larger diameter for placement or implantation in thevasculature, often by the balloon portion of the catheter. Stentsdelivered to a restricted coronary artery, expanded to a larger diameteras by a balloon catheter, and left in place in the artery at the site ofa dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer; U.S.Pat. No. 5,007,926 to Derbyshire; U.S. Pat. No. 4,733,665 to Palnaz;U.S. Pat. No. 5,026,377 to Burton et al.; U.S. Pat. No. 5,158,548 to Lauet al.; U.S. Pat. No. 5,242,399 to Lau et al.; U.S. Pat. No. 5,344,426to Lau et al.; U.S. Pat. No. 5,415,664 to Pinchuk; U.S. Pat. No.5,453,090 to Martinez et al.; U.S. Pat. No. 4,950,227 to Savin; U.S.Pat. No. 5,403,341 to Solar; U.S. Pat. No. 5,108,416 to Ryan et al.,U.S. Pat. No. 5,242,451 to Harada and European Pat. No. Application No.707 837 A1 to Sheiban, all of which are incorporated herein byreference. A stent particularly preferred for use with this invention isdescribed in PCT Application No. 960 3092 A1, published Feb. 8, 1996,the content of which is also incorporated herein by reference.

The present invention is particularly directed to improved arrangementsfor catheters of reduced profile for performing angioplasty and forreleasably attaching the stent to the catheter to facilitate deliverythereof. The invention is applicable to all the various types ofcatheters used in such procedures, including rapid exchange types andover-the-wire types.

The various embodiments of the invention disclosed herein are shown inschematic form for clarity and simplicity of illustration. It isanticipated that those familiar with this art will be able toincorporate the invention into actual catheters without difficulty.Similar elements in the Figures are identified by similar or identicalnumbers.

SUMMARY OF THE INVENTION

This invention concerns catheter apparatus suitable for performingangioplasty and for delivery of stents to body cavities. In general,stents are prosthetic devices which can be positioned within a bodycavity, for example, a blood vessel or in some other difficultlyaccessible place of the body of a living human or animal. The stentprosthesis is formed of a generally tubular body, the diameter of whichcan be decreased or increased. Stents are particularly useful forpermanently widening a vessel which is either in a narrowed state, orinternally supporting a vessel damaged by an aneurysm. Such stents aretypically introduced into the body cavity by use of a catheter. Thecatheter is usually of the balloon catheter type in which the balloon isutilized to expand the stent, which is positioned over the balloon fordelivery, to place it in a selected location in the body cavity. Thepresent invention is particularly directed to improved arrangements forreleasably attaching the stent to the catheter to facilitate deliverythereof. The stent is held in place on the catheter by means of anenlarged mounting body carried within the balloon by the catheter shaftto which the stent and balloon are fitted. The stent is fitted over theballoon, as by crimping. However, according to the invention in someembodiments, the enlarged body is axially movable on the inner shaft ofthe catheter so that it can be retracted from the stent mounting area toprovide a small profile for performing angioplasty. The catheter canthen be withdrawn; the enlarged body can be moved into the stentmounting area; the stent can be mounted and the catheter can bere-inserted to implant the stent. In other embodiments, the enlargedbody can be arranged to be reducible and enlargeable in size rather thanbeing movable. Alternatively, the movable mounting body may be carriedoutside the balloon.

A catheter of this type makes possible a method in which, before stentloading with the associated mounting body arranged to provide reduceddiameter in the balloon region, the catheter may be used to dilate alesion or the like. The catheter may be withdrawn and the mounting bodymay then be selectively manipulated to provide an enlarged diameter inthe stent mounting region and a stent may be loaded onto the catheter.The catheter may be re-inserted to implant the stent. The catheter maybe withdrawn or left in situ and the mounting body may be manipulated toprovide reduced diameter again and the catheter may be used for anypost-dilation desired. Also, the catheter may be used multiple times inthe procedure for dilation and stent implantation.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an isometric view, a portion of which is enlarged and inlongitudinal section, of a balloon catheter having a mounting body in aretracted position;

FIG. 2 is an even more enlarged view in longitudinal cross-section ofthe distal end portion of the catheter of FIG. 1;

FIG. 3 is similar to FIG. 2 but showing the mounting body advanced toreceive a stent mounted on the balloon;

FIG. 4 is an enlarged cross-sectional view of the distal end portion ofthe catheter of FIG. 1 similar to that of enlarged view FIG. 3 butshowing the balloon in an expanded condition along with the expandedstent;

FIG. 5 is a schematic showing of a preferred mounting body carried bythe catheter shaft within the balloon, the body being spirally cut toimprove flexibility;

FIG. 6 is a schematic showing in cross-section of another embodiment ofthe invention with a mounting body positioned to receive a stent butwith a stent not yet mounted;

FIG. 7 is a schematic showing of another embodiment of the invention;

FIG. 8 is a schematic showing of a means for conveniently crimping thestent on the embodiment shown in FIG. 5;

FIG. 9 is a schematic showing of yet another embodiment of theinvention;

FIG. 10 is a showing of another embodiment of a mounting body accordingto the invention;

FIG. 11 is a schematic of an enlargeable mounting body which is notaxially movable;

FIG. 12 is a schematic of an alternate enlargeable mounting arrangementwhich is not axially movable;

FIGS. 13 and 14 are schematic showings of yet another embodiment inwhich the axially movable mounting body is carried outside the balloon;

FIGS. 15 and 16 are schematic showings of still yet another embodimentof the invention, and

FIGS. 17 and 18 are a modified version of the embodiment shown in FIG.11.

FIGS. 19 and 20 are modified versions of the embodiment shown in FIG.11.

FIG. 21 shows a version of the embodiment shown in FIG. 11 in which asyringe is inserted into the distal end of the liner of the catheter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-4 an angioplasty and stent delivery catheter systemgenerally indicated at 10 includes a balloon catheter 12 having aballoon 14 on a distal end portion generally indicated at 16. FIG. 1shows a proximal portion of the catheter at 12a and a distal portion 12bin enlarged view. FIGS. 2 and 3 show the distal end portion 16 in aneven more enlarged view. The illustrative catheter 12 is of the typeknown as a rapid exchange or single operator catheter. However, othertypes of catheters may be used, such as over the wire and fixed wiretypes. The balloon 14 is fixed to the catheter 12 by standard means. Theballoon is shown in its contracted state in FIGS. 1-3. In FIGS. 1 and 2the catheter is shown prepared for performing angioplasty and in FIG. 3it is prepared for stent implantation.

In FIGS. 1 and 2, an axially movable mounting body 30 is shown in aposition proximal to the end portion 16 of the catheter where a stentmay be mounted. The catheter includes at its proximal end a manifold,generally designated 13, as is known in the art. The manifold includesan inflation port 15 as is known in the art. A wire 31 is attached tobody 30 to enable remote (from the proximal catheter end) advancementand retraction of it axially on inner lumen 26 over which it slides. Inthe retracted position shown in FIGS. 1 and 2, the catheter has a lowprofile for performing angioplasty.

This position is a retracted position and is selected by operation of apull wire 31. The retracted position of the mounting body may vary. Tomaximize the low profile of the distal end 16 of the catheter, theretracted position may be within the outer member 24.

After such a procedure, the balloon is deflated, the catheter iswithdrawn and the mounting body is advanced by means of wire 31 to thestent mounting position shown in FIG. 3. A stent 18 may then be fixedabout the deflated balloon by crimping it thereto. The stent has alarger expanded diameter which is obtained when the balloon is againexpanded in the known manner. That is, the stent is released from thecatheter upon expansion of the balloon as shown in FIG. 4 to be placedin a vessel at the desired location. When the balloon is then againdeflated, removal of the balloon and catheter may be accomplished,leaving the stent in place. Exemplary dimensions for the inner 26 is adiameter of 1/2 mm and for body 30 a diameter of 3/4 mm.

As is known in the art the balloon is either bonded at its ends byadhesive 20 and 22, respectively to the outer member 24 of the catheterand to the inner member 26 of the catheter in the manner as shown, or ismade one-piece with the outer member as is known in the art. Thecatheter balloon may be inflated by fluid (gas or liquid) from aninflation port extending from a lumen 28 (seen in FIG. 2 and 3)contained in the catheter shaft and opening into the balloon as shown,or by other known arrangements, depending on the design of the catheter.The details and mechanics of balloon inflation and specific overallcatheter construction will vary according to the particular designinvolved in any given instance, and are known in the art per se. Suchdetails are only shown schematically herein. All variations areacceptable for use with this invention.

Any balloon expandable stent may be used with this invention. Many areknown in the art including plastic and metal stents. Some are more wellknown such as the stainless steel stent shown in U.S. Pat. No.4,735,665; the wire stent shown in U.S. Pat. No. 4,950,227; anothermetal stent shown in European Pat. No. Application EP 0 707 837 A1 andthat shown in U.S. Pat. No. 5,445,646, or U.S. Pat. No. 5,242,451. Allof these patents are incorporated herein by reference. Also, shapememory metal stents may be used. As already indicated the stent of PCTApplication 960 3092 A1 is particularly preferred.

The stent is typically for example about 16 mm long, while the balloonmay be 20 mm long for example. These dimensions, however, are merelyrepresentative for illustrative purposes only and are not meant to belimiting. The stent is positioned over the balloon portion of thedilatation catheter and gently crimped onto the balloon either by handor with a tool such as a pliers or the like to be mounted for deliveryas shown in FIG. 3. The crimping may be readily accomplished by thephysician during the procedure.

In accordance with this invention, mounting body 30, best seen in FIGS.2 and 3, is included inside balloon 14 to provide a cushion and/orsubstrate of enlarged diameter relative to the stent to support and holdthe stent and secure it during crimping and the delivery procedure. Themounting body may be axially movable proximally or distally from theposition shown in FIG. 3, proximally being preferred.

In the embodiment shown in FIGS. 1-3, mounting body 30 is cylindrical inform and takes the shape of a sleeve axially and slidably carried oninner lumen 26, providing an enlarged area or portion for receiving theballoon and stent when the latter is crimped to the balloon. Marker band34 may also be included on inner 26 as shown. Any radiopaque materialsuch as gold is useful for this purpose. A stop member 36 of generallyconical shape or any other shape may also be included on the marker band34 as shown to provide additional resistance to stent movement duringdelivery and to protect the leading edge of the stent during delivery.Polyethylene or the like is suitable for the stop member. Other markerarrangements and stop arrangements may be used as well.

Although, the material of the mounting body may be hard, it ispreferably of any deformable thermoplastic material, preferably anelastomer material and more preferably of a relatively resilientelastomer material, e.g., lower durometer silicone. A preferreddeformable thermoplastic material is high density polyethylene (HDPE). Apreferred lower durometer silicone is in the form of tubing. Thedeformation of the resilient material of the mounting body when thestent/balloon is crimped to it causes a radial outward force on thestent/balloon increasing the friction therebetween despite any recoil ofthe stent.

During stent delivery, the balloon catheter is advanced through andpositioned in a patient's vasculature so that the stent is adjacent tothe portion of the vessel where treatment is to take place. The balloonis inflated to expand the stent to an enlarged diameter. When the stenthas reached the desired diameter, the balloon is deflated so that thecatheter may be removed leaving the stent in place.

Another embodiment of the invention is shown in FIG. 5. In thisembodiment mounting body 30 is a spiral cut elastomer or other suitablematerial, such as a rigid or flexible plastic, to provide separation forflexibility in that portion of the catheter, allowing more easy movementor tracking around bends. The spiral cut may be only partly through themounting body or may be all the way through as shown in FIG. 5. Also,while stop member 36 is shown at the distal end portion of the catheterin this embodiment, no stop member may be used.

Another similar version is shown in FIG. 6 which includes a cylindricalmounting body 30 made up of a plurality of separate adjacent rings 30aheld together by wire 31 which extends therethrough as shown with stops29 to secure the rings together. Rings 30a may be individual bodiescarried on the sheath or bodies cut from a cylinder to partiallyseparate them or fully separate them. Suitable arrangements may be madeto wire 31 at each end of the body 30 to hold the rings together, asshown.

The embodiment shown in FIG. 7 includes another feature based on thegeometry of the mounting body for further securing the stent uponcrimping. This feature is referred to herein as "interlocking". That is,the stent may be interlocked to the mount so that the stent cannot slideproximally or distally on the balloon unless it is deformed, such as byexpansion. This can be seen by perusing the structure shown in FIG. 7which includes the inner 26 having a two-piece mounting body made up ofspaced mounting bodies 30a and 30b. These bodies are connected to eachother by connection means 33 which may be a separate or integralcylindrical body of lesser diameter or may be one or two or morerelatively rigid wire members as shown. The spacing between bodies 30aand 30b allows portions of the stent 18 and balloon 14 to be depressedor inserted between the bodies upon crimping of the stent thus formingan interlock against sliding of the stent axially or longitudinallybefore the stent is released.

The interlock formation or crimping is readily accomplished by anysuitable means such as a two-piece die 40 shown in FIG. 8 or the like.

FIG. 9 demonstrates that more than a two-piece mounting body arrangementmay be used if desired. In this embodiment, the mounting body iscomprised of three spaced interconnected bodies 30a, 30b and 30c on theinner 26. Preferably in the embodiments of FIGS. 7 and 9, the mountingbodies will be ring-like in shape or cylindrical in shape although otherconfigurations will be readily apparent to those familiar with this art.

Referring now to FIG. 10, another embodiment of a movable mounting body30 is shown in the form of a rigid coil of plastic, metal or the likehaving a control wire 31, preferably integral therewith. When in themetal form, the coil may be coated with a polymer such as polyethyleneor PTFE or enclosed in a polymeric sheath of similar material. The coilmay be slidably received on the inner 26 similar in arrangement to thatshown in the preceding Figures.

As already indicated, an alternate arrangement may be used in which themounting body, instead of being movable, is designed to be enlargeableand reducible or collapsible, while remaining in a fixed position in thestent mounting area of the catheter. FIGS. 11 and 12 are directed tosuch an arrangement.

In FIG. 11, an inner balloon 50 of smaller diameter than outer balloon14 is mounted on the inner 26. Balloon 50 may have a separate inflationconduit 52 inside inner 26, preferably including a valving arrangement54. Valve 54 may be a one-way valve allowing only inflation of balloon50 if desired. However, inner 26 may serve as the inflation conduit aswell. In addition to fully inflat the balloon, inner balloon 50 may alsobe partially inflated.

FIG. 19 shows a modification to FIG. 11 in which two inner balloons 50aand 50b are included. FIG. 20 shows a modification in which twoinflation valves 54a and 54b are included.

FIG. 21 shows a full arrangement of inner balloon 50 in which a syringe120 is inserted into the distal end of the liner 26 of the catheter. Thesyringe has at its ends blocks 122 and 124 to enable localpressurization of inner 26 to inflate balloon 50.

FIGS. 17 and 18 show an inner balloon 50 similar to the arrangement ofFIG. 11 but the balloon 50 in FIG. 17 has a narrow center portion andwide ends to provide a mounting shape similar to that of FIG. 7. In FIG.17, balloon 50 is inflated and balloon 14 is partially inflated. In FIG.18, balloon 50 is inflated and balloon 14 is uninflated ready for stentloading. Balloon material is preferably a polyethylene or urethaneelastomer such as Tecoflex or Tecothane from Thermedics.

Referring to FIG. 12, an alternate embodiment is shown in which theproximal portion of the inner 26 is axially movable while the distalportion 26b is fixed with respect to the catheter. In between portion26a and portion 26b is a coil spring 60 inside a flexible sheath 62 ofPTFE or the like. Portion 26b of the inner is attached to balloon 14 atthe very distal end portion of the catheter. Portion 26a is movableaxially within the outer 22. Thus, if 26a is pushed in the distaldirection and held to compress coil 60, the coil will enlarge indiameter to provide an enlarged mounting area for a stent. Twisting theinner to twist the coil will enhance enlargement. Alternatively, coilspring 60 may be replaced by a braided element.

Also, by providing different pitch over the length of the coil it can bemade to enlarge more in some regions than in others. For example, if thecoil windings are closer together in the center portions than in the endportions, when the coil undergoes compressing, the two end portions willenlarge in diameter more than the center portion to provide a mountsimilar to that of FIG. 7.

Referring now to FIGS. 13 and 14, another embodiment is shown which isalternative to the earlier described embodiments which are inside theballoon on the catheter. In this embodiment a sheath 80 is carried onthe outside of the catheter. Sheath 80 is elastomeric and is axiallymovable from a stent mounting position as shown in FIG. 14 to a positionremote from the stent mounting position, such as the retracted positionas shown in FIG. 13. In the position shown in FIG. 13, balloon 14 may beinflated and deflated. In the position shown in FIG. 14, balloon 14 willbe deflated for low profile. Sheath 80 when over the balloon as in FIG.14 acts to increase the profile of the catheter to facilitate crimping astent thereto during deployment of the stent, sheath 80 will expand withballoon 14 to facilitate inflation and during deflation the elastomersheath will return to its original dimension. An elastomer materialwhich is presently preferred is Tecothane, a tradename for athermoplastic polyurethane available from Thermedics, Inc., of Woburn,Mass. It may be about 0.003 inches thick, for example.

With respect to FIGS. 15 and 16, a further embodiment of the inventionis shown in which inner 26 carries a mounting body 30, the distal end100 of which is secured or fixably attached to inner 26, as by anysuitable adhesive. The remainder of body 30 is slidable over inner 26 asby the application of compression in the distal direction at theproximal end 102. This may be accomplished by push wire 104 whichextends to the proximal end of the catheter for remote manipulation asis known in the art.

Mounting body 30 is accordion folded with more widely spaced folds atthe end portions 106, than at the central portion 108. Thus, as can beseen in FIG. 15, a relatively low profile is provided withoutcompression for normal angioplasty use. When a stent is to be mounted(not shown), compression by means of push wire 104 will result in aconfiguration of enlarged diameter of body 30 as shown in FIG. 16 toprovide a mount similar to that of FIG. 7 in general configuration. Ifthe spring is uniform over the body, it sill enlarge uniformly, similarto the inner balloon of FIG. 11. The Figures are schematic in form butthe concept can be readily appreciated.

As an alternative to a folded construction, the body may be of braidedconstruction to achieve the same operation.

Also, this form of body 30 may be inserted into a two piece inner 26similar to the arrangement shown in FIG. 12. In all of thesearrangements, the accordion folded body material may be of any suitablepolymer, such as polyethylene. For example, tubing having a wallthickness of about 0.002 inches may be used. The accordion folds orpleats may be readily formed in such tubing by means of a pressure moldcontaining spaced blades placed in a heated chamber.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is as follows:
 1. A stent delivery system comprising acatheter having a shaft and an inflation means associated therewith at adistal part of the shaft and including mounting and retaining meansconstructed and arranged to receive a stent, the stent having a length,wherein the stent is crimped on the expandable means for radialexpansion of the stent, the mounting and retaining means beingassociated with the inflation means and being constructed and arrangedfor selectively providing an enlarged mounting body between theinflation means and the shaft and within the inflation means forreceiving the stent thereon, wherein the enlarged mounting body has alength which is substantially the same length as the stent.
 2. A stentdelivery system comprising:a catheter having a shaft and an expandableinflation means associated therewith at a distal part of the shaft andincluding a mounting and retaining means capable of receiving a stent,the stent having a length, wherein the stent is crimped onto theexpandable inflation means and directly on the mounting and retainingmeans, whereby the stent may be radially expanded upon inflation of theinflation means, the mounting and retaining means comprising a mountingbody having a length, the mounting body being substantially the samelength as the stent and being carried on and surrounding the shaftinside the inflation means, whereby the diameter of the shaft and thediameter of the expandable inflation means are selectively increased atthe distal part of the shaft for facilitating the mounting and retainingof the stent.
 3. The delivery system of claim 2 wherein the mountingbody is axially movable with respect to the inside shaft, and includingmeans for moving the mounting body.
 4. The stent delivery system ofclaim 3 wherein the mounting body is positioned to receive a stent and astent is crimped to the mounting and retaining means over the balloonfor delivery.
 5. The stent delivery system of claim 3 wherein themounting body is of a material which resiliently deforms under radialpressure.
 6. The stent delivery system of claim 5 wherein the materialis elastomeric.
 7. The stent delivery system of claim 5 wherein thematerial comprises high density polyethylene.
 8. The stent deliverysystem of claim 5 wherein the material comprises silicone.
 9. The stentdelivery system of claim 2 including a stop positioned at the distalpart of the shaft which includes the inflation means and carried by theshaft inside the inflation means.
 10. The stent delivery system of claim2 including at least one marker band fastened to an inner lumen.
 11. Thestent delivery system of claim 2 wherein the inflation means comprises aballoon.
 12. The stent delivery system of claim 2 including a stoppositioned at the distal part of the catheter and carried by the shaftinside the inflation means.
 13. A method of altering the configurationof a balloon catheter of variable profile for improved mounting of astent on the balloon catheter and thereby providing a catheter formultiple use, comprising the steps of:providing a balloon catheter ofrelatively low profile adapted and rearranged for use in an angioplastyprocedure; sliding a stent mounting body on the catheter to a positionassociated with the balloon such that the stent mounting body has alength and is positioned on the catheter within the balloon forreceiving a stent and enlarging the catheter profile at that position,and mounting a stent, having a length, on the balloon and the associatedstent mounting body at that position of the stent mounting body, whereinthe mounting body has substantially the same length as the stent.